There are fundamentally two categories of musical synthesizers: (a) samplers (or “sampling synthesizers”), in which stored digitized recordings (or samples) of actual instruments are reproduced when notes are played on a keyboard connected to the sampler, and (b) synthesizers, in which sounds are created at the time they are played based on analog or digital electronic circuitry which creates the sound without reliance upon previously recorded actual instruments. These instruments today are predominantly polyphonic, meaning they can play more than one note at a time. While the nature of the invention is immediately more applicable to samplers, it will function in connection with synthesizers as well. For simplicity the discussion herein will focus primarily on sampling applications.
When samples are initially recorded, there may be one or many instruments actually playing the sound (and each may be playing one or more notes). Typically with orchestral or large band sounds, entire sections of instruments play each sampled note, with all instruments in a given section concurrently playing a single note. Thus, in the prior art a sample of an orchestra section of eight cellos would be a single recording of eight cello players playing the same note. When this sample of one note is played back on a sampler, all eight instruments are heard playing the same note. Similarly, a sample of an orchestra section of sixteen violins would be made by recording sixteen individual violin players all concurrently playing the same note, and when this sample is played back the sound of all sixteen violins would be heard playing that note concurrently.
Depending upon the nature of the technology used in a prior art sampler, there may be a separate source recording (initial sample) in its library for each note the sampler is capable of reproducing, or a single note sample may be electronically interpolated to higher and lower pitches corresponding to various notes. The first option yields optimum sound quality, at maximum cost and complexity, to create the library and reproduce it in the sampler, whereas the second option yields lesser sound quality at a reduced cost and complexity.
In the prior art, when multiple notes are concurrently played on a sampler, multiple instances of the sampled recording are sounded. Thus, if one has a cello sample in the library made from eight cellos, and two notes are played together on the sampler, the sampler would play the sound of sixteen cellos playing, eight instruments per note. If one plays a triad (i.e., three notes concurrently) on the sampler, the sampler would play the sound of twenty-four cellos (i.e., three times the eight cellos per sample). This is called additive polyphony. Although this is what is available in professional studios, it results in an unrealistic sound quality which does not reflect how an actual orchestra would sound. By way of example, with a real orchestra, the power (or volume) of a cello section stays relatively constant whether the cello players play one or several notes simultaneously (e.g., the power is about the same whether eight cellists of an eight cello orchestra section all play the same note or if five are playing one note while three are playing a different note). With a prior art sampler, the power is multiplied approximately by the number of notes played. By way of another example, as more and more notes are played simultaneously with a sampler, the density of the harmonics sounded tends to create an organ-like effect rather than preserve the clarity and concise sound definition afforded by a reasonable and fixed number of instruments playing at once. (Note that there may be valid reasons to use additive polyphony, but optimum orchestral sound is not obtained using additive polyphony exclusively.)